Posted by: Jack Mankin (MrBatspeed@aol.com) on Sun Feb 14 15:11:40 2010

>>> Hey Jack

Question for you is at what point in the swing do the hands seperate from shoulder rotation or from hip rotation? These are two seperate questions which in one. By the word seperate I mean at what point do the hands rotate either slower or faster then the hips or the shoulders and do they at any time change their circle around the tilted axis of the spine?

Any comments would be great. <<<

Hi Dave

Early in my study of the swing, I collected over a hundred overhead views of the swings taped from games in the old Astro Dome. Charting the hand-path of these swings presented me with one of the first fallacies to the mechanics that I (and most all coaches) had taught for decades. We were all taught that "The shortest distance between two points was a straight line" and therefore the hands should take an "A to B" path.

Note: I use the term "charting" because at the time of my study, I did not have Motion Analysis Software. I placed a sheet of clear plastic over a TV screen and traced with a grease pencil as I advanced the frames with a VCR

Since we believed an "A to B" hand-path to be most productive, we referred to batters whose hands followed a more circular path as having a "casting" problem. We used drills, like the "Fence Drill," and cues like "Keep your shoulder in-there" to straighten out their problem.

Studying the charted hand-paths of these MLB hitters caused a knot to form in my gut -- "What had I done to those kids I had coached?" Not only did these MLB hitters' hands not take a linear path, the more circular the path, the higher they placed in the batting stats. Batters with less arc placed much lower than those we might think of as "casters."

Dave, I think the next step in my study of these over-head views may address your question - What is the relationship between the angular displacement rate of the hand-path to shoulder rotation? This lead to the second fallacy I had taught, "Keep your shoulder in-there" during the swing.

Charting the angular rate of displacement of the hand-path to that of the shoulders provided two important points. (1) Right from initiation, the lead-shoulder rotated at about the same angular rate as the hands. (2) Both rotated through the same (or close to it) number of degrees - from 145 to 155 degrees.

To obtain this data, I traced a line from the spine (middle of the neck) to both the lead-shoulder socket and the hands (center of) at launch and then at contact. As I stated, both rotated at about the same rate through the same number of degrees. -- Although the video below addresses "Front compared to Rear shoulder rotation," it should help show how I obtained the above data.

Rose - Shoulder Rotation Comparison

Jack Mankin